New Holland T8010 Manual page 793

16
1. SIGNAL LINE PRESSURE
2. PUMP CASE DRAIN
3. CONTROL PISTON PRESSURE
4. PISTON PUMP OUTLET PRESSURE
PFC Axial Piston Pump - Operation
Low Pressure Standby
When there is no demand for flow, there is no pressure signal feed back to the pump and the pump will go to the
low pressure standby mode. As there is no place for the oil from the pump to flow, the pump will build pressure in
the pump outlet passage. This pressure is directed through internal passages in the piston pump back plate to the
end of the pump compensator spool opposite the spring.
The spring acting on the flow compensator spool, is set to allow the spool to move at a 340 to 390 psi (23.5 to 27
bar) differential pressure. The flow compensator spool will then move down to allow the oil to flow into the passage
leading to the pump control piston.
The pressure acting on the pump control piston tilts the pump swash plate against the swash plate control spring,
to a near neutral position. In this condition, the pump will provide just enough flow to make up for internal leakage,
thus maintaining a minimum system pressure of 340 to 390 psi (23.5 to 27 bar).
The pump will remain in the low pressure standby position as long as there is no pressure or flow demand from the
hydraulic system. In this mode, the pump produces very little heat and absorbs very little horsepower from the
engine. This is one of the outstanding features of the PFC axial piston pump.
Section 35 - Hydraulic Systems, 3PT - Chapter 2
18
15
4
3
14. OUTLET PORT (NOT SHOWN)
15. FLOW COMPENSATOR SPOOL
16. HIGH PRESSURE COMPENSATOR SPOOL
17. HIGH PRESSURE SPRING
19
21
1
2
35-2-36
17
18. FLOW COMPENSATOR SPOOL
19. HIGH PRESSURE COMPENSATOR SPOOL
21. COMPENSATOR ASSEMBLY
RH02B010